Poly(lauryl methacrylate) (PLMA) thin film doped with Mn:ZnSe quantum dots (QDs) was spin-deposited on the front surface of Si solar cell for enhancing the solar cell efficiency via photoluminescence (PL) conversion. Significant solar cell efficiency enhancements (approximately 5% to 10%) under all-solar-spectrum (AM0) condition were observed after QD-doped PLMA coatings. Furthermore, the real contribution of the PL conversion was precisely assessed by investigating the photovoltaic responses of the QD-doped PLMA to monochromatic and AM0 light sources as functions of QD concentration, combined with reflectance and external quantum efficiency measurements. At a QD concentration of 1.6 mg/ml for example, among the efficiency enhancement of 5.96%, about 1.04% was due to the PL conversion, and the rest came from antireflection. Our work indicates that for the practical use of PL conversion in solar cell performance improvement, cautions are to be taken, as the achieved efficiency enhancement might not be wholly due to the PL conversion.

Patterned magnetic thin films have for the first time been used to orient and retain micron-sized III-V elements on silicon substrates during fluidic hybrid assembly. Modeling of the forces between Ni thin films patterned on one surface of 5-6 m target areas on Si substrates predicts that the strength and fall-off characteristics of the attractive forces can be engineered to orient and securely retain only pills that are right side up. Verification of this behavior has been obtained by assembling 50ϫ 100 m 2 micropills in recesses with patterns of Sm-Co rectangles.

Photoluminescence (PL) conversion of Si nanoparticles by absorbing ultraviolet (UV) lights and emitting visible ones has been used to improve the efficiency of crystalline Si solar cells. Si nanoparticle thin films are prepared by pulverizing porous Si in ethanol and then mixing the suspension with a SiO 2 sol-gel (SOG). This SOG is spin-deposited onto the surface of the Si solar cells and dries in air. The short-circuit current as a function of Si nanoparticle concentration is investigated under UV illumination. The maximal increase is found at a Si concentration of 0.1 mg/mL. At such concentration and under the irradiation of an AM0 solar simulator, the photoelectric conversion efficiency of the crystalline Si solar cell is relatively increased by 2.16% because of the PL conversion.OCIS codes: 310.6628, 310.6860, 350.6050, 160.4236. doi: 10.3788/COL201210.063101. The use of solar cells as electric power supply is one of the solutions to the problems of increasing global energy consumption and decreasing fossil fuel storage [1] . Moreover, it is almost the only energy source for satellites, space stations, and other outer space exploration activities [2] . Currently, commercial solar cells normally utilize a narrow band of solar emission spectrum, i.e., from visible to near-infrared regimes, because of the bandgap limitations of the related semiconductors, such as Si, GaAs, CdTe, and CuIn 1−x Ga x Se 2 [3,4] . Thus, the main approach in improving the performance of the current solar cells is the use of upconversion films to convert infrared lights into visible ones and thus increase the absorbed light flux of a solar cell [3−6] . However, the upconversion probability is so low that its practical application is still currently unavailable. Another approach is the use of downconversion and photoluminescence (PL) conversion mechanisms to convert ultraviolet (UV) lights into visible ones for the same purpose [3−12] . Although the quantum efficiency of downconversion for current materials could be high, the wavelength range of UV light to be downconverted is usually from 100 to 200 nm, which is hardly covered by the solar spectrum. The PL conversion probability can be on the order of 10% [3,13,14] compared with that of upconversion, which is less than 0.1%. Thus, PL conversion is practically and technically important particularly for solar cells used in the outer space and highlands because the amount of UV light (∼ 250 nm < λ < 390 nm) from the sun is relatively high [9−12] . During the investigation of Si nanoparticle light emissions, Si nanoparticles were found to absorb UV light and emit red or near-infrared ones [9−14] . This feature of PL conversion can be used to improve the performance of crystalline Si solar cells [9−12] , particularly the dominant ones in the market today, which absorb red light most efficiently. In this letter, the correlation between the PL emissions of Si nanoparticles dispersed in SiO 2 and the short-circuit current of crystalline Si solar cells was first studied under UV ligh...